What is Keepin' Lean Up In My Cup?
1.
Lean:
Codeine syrup available only with a prescription, see also sipping lean. It is called "lean" because that is what drinking it makes you do.
So basically, "keepin lean in your cup" means keeping your cup filled with codeine syrup.
Smoking out, throwing up, keepin' lean up in my cup, all my car got leather 'n wood, in my hood we call it buck. -- Jay-Z featuring Bun B and Pimp C (Big Pimpin')
See